Preliminary Remark—the invention presented herein after would be described in terms of applications referring to agricultural irrigation with water. However, any professional in this field would understand that the invention is not restricted solely to this field, but rather the invention is also applicable to drip emitters that are employed in other fields, such as, for example—wetting and flushing (rinsing) minerals with water or using various different liquids that are not water (for example detergents, or water containing fertilizing materials).
As is well known and recognized from earlier times, there exist drip emitters that are used in agricultural irrigation systems that incorporate in them a mechanism for regulating their throughput quantities (flow rate). The water pressure arriving at the drip emitters is not constant, but rather varies in accordance with the pressure variations in the deployed water supply conduit unto which they are connected. Such variations in water pressure occur, for example, due to pressure variations in the source supplying the water to the conduit, the relative locations of the drip emitters or the varying topography of the landscape upon which the irrigation system is deployed (e.g. mountains, slopes, hills, valleys and similar variables). A regulating mechanism based on an elastomer component enables to increase or decrease the water flow to the output (exit) opening from the drip emitter, exploiting the movements of the elastomer component in accordance with the water pressure prevailing in the conduit. The differential regulation principle might be implemented in these drip emitters, wherein the elastomer component is exposed—on its one side, to the water pressure prevailing in the conduit and on its other side to the reduced pressure of the water, as it flows inside the drip emitter towards the water outlet opening (for example—the reduced water pressure after the water exited from a throttle means of the kind resembling a labyrinth like flow passage installed in the drip emitter). Thus, by integrating a regulating mechanism into the drip emitter, it becomes possible to maintain an essentially constant flow rate through the drip emitter, of the kind best suited for optimal irrigation conditions, independently from variations in the water pressure that, as said, occur in the water supply conduit.
Drip emitters that incorporate in their structure a regulating mechanism that is based on an elastomer component together with a throttle means, are installed in agricultural irrigation systems in a variety of modes—inside the water supply conduit and as an integral part thereof, or as discrete units located between sectors of the conduit along its length, or just as separate units that are stuck into—or connected to—the conduit from the outside.
Irrigation systems utilizing drip emitters pose an additional challenge. This is having the capability to prevent water run off and emptying of the water supply conduit at the time the irrigating action stops and until the next irrigation cycle (a property that would prevent loss of water and the need to build up anew, from the beginning, the required pressure in the conduit when renewing the irrigation). It also contributes to prevent sucking contaminations into the drip emitter and the water supply conduit when the pressure drops in the conduit.
Also well known and recognized from earlier implementations, are those regulated drip emitters in which the elastic properties of the elastomer component (or in other words, the membrane) used in them in the regulating mechanism, are also implemented for creating tight sealing at the water inlet (entrance) opening, and this from the instant that the water pressure in the water supply conduit drops to below a pre set threshold level, or—in other words, exploiting the regulating mechanism's membrane also for generating a non-drain valve. Such an implementation for a drip emitter is described for example in Mehudar's patent U.S. Pat. No. 5,279,462 that describes a regulated drip emitter of the type being stuck and connected to the water supply conduit from the outside, wherein it also includes a non-drain valve.
Referring to FIG. 1a. This figure constitutes a general schematic view of a drip emitter 10 in accordance with the above cited prior art. Drip emitter 10 includes a water inlet opening 11 that is connectable unto a water flow passage to the drip emitter from the water supply conduit (that is not illustrated), a water outlet opening 13 that is connectable to a water flow passage from the drip emitter towards the surface area intended to be irrigated, and a throttle means 15 for reducing the water pressure, the latter is connected to a water flow passage from the water inlet opening 11 and—after the water pressure is reduced, to the water outlet 13, and an elastomer component 17 that constitutes the regulating membrane 19 whose one side is exposed to the water pressure prevailing in the water supply conduit and whose other side (of the membrane) is exposed to the pressure prevailing at the water outlet—so that regulating membrane 19 is movable in accordance with the differential water pressure prevailing on the two sides of the membrane in order to narrow or widen the dimensions of water flow passage 21 towards water outlet 13.
A constructional characteristic of drip emitter 10 is the utilization of the same component—namely the elastomer component 17, also for producing the non-drain valve 23. This is achieved by biasing regulating membrane 19 towards inlet opening 11, from the instant that the water pressure in the conduit drops below a pre set threshold value. Removing the sealing from the non-drain valve 23 and enabling flow passage stream through it is dependent on the capability of the force exerted by the water pressure prevailing in the water supply conduit to overcome at first the strain by which membrane 19 was biased towards water inlet 11, and eventually—in order to maintain the non-drain valve at its open state, it depends also on the force exerted by the reduced pressure of the water over the other side of the same membrane itself after it passes through throttle means 15.
It was found that a distinguished advantage of the implementation of the differential regulating principle in drip emitters, well known from days yore, unluckily contradicts with the assimilation of the non-drain valve mechanism in those same drip emitters, and this especially when it is desired to have the same elastomer component itself serve also for executing the regulating action, namely to act both for creating the regulating action and providing the sealing of the non-drain valve.
The differential regulating principle imparts an advantage as it provides self rinsing or flushing of contaminants from the drip emitter. This applies to those contaminants that “succeeded” in passing through the filter routinely installed at the inlet opening of the drip emitter, and wherein these contaminants were also smaller than the dimensions of the minimal flow path that is formed in the drip emitter's throttle means. Such contaminants are swept and raked towards the water outlet opening of the drip emitter. The drip emitter's regulating mechanism is built so that at the time it is operating, the size of the flow passage that remains open towards the water outlet opening is of the order of magnitude of hundredths of a mm. Since these contaminants are larger than this narrow passage, a clog is formed. But this clog immediately causes an increase of the water pressure in the area in the vicinity preceding the clog location. Due to the water pressure prevailing in the water inlet, which is relatively higher compared to the reduced water pressure after the water passed through the throttle means, the membrane is regularly stressed and driven to reduce the dimensions of the water flow passage towards the water outlet. But, due to the sudden pressure increase upon clogging, the membrane would then tend to retreat a little. This withdrawal of the membrane causes momentarily increases in the dimensions of the flow passage and enables flushing of the contaminants towards the water outlet. Any professional in this field would also understand that such a self flushing phenomena is also occurring at the stage of the gradual build up of the water pressure in the water supply conduit, as well as at the stage of closing the water source and the decrease of the pressure in the conduit (the stage at which the membrane reverts to its “paused” state, while opening the flow passage towards the water outlet of the drip emitter to its maximum size).
Exploiting the self rinsing or flushing phenomena as explained above, requires—naturally, advanced and accurate designing of the membrane—from the point of view of both structural and geometrical aspects. In order to enable such a self rinsing phenomena, the membrane has to retreat at least back to the point of providing a minimal flow passage equal to the one that is formed in the throttle means of the drip emitter (as obviously the contaminants that passed the throttle means might be of the same size). Concurrently, as a design principle, it is customary to try and increase the size of the minimal flow passage formed in the drip emitter's throttle means as much as practicable (in order to prevent generating the clog already inside the throttle means), and obviously such a design goal leads to necessitating a larger retreat step of the membrane (at least during the gradual build up stage of the water pressure in the conduit and also in the stage of shutting down the water source with the ensuing result of pressure drop in the conduit).
Supposing that in accordance with the prior art detailed above it would be desired that the same elastomer membrane component would serve for both performing the regulating action and as a seal in the non-drain valve, then—in order to obtain the biasing of the membrane against the water inlet of the drip emitter (as required for obtaining sealing and prevention of water run of), it is necessary to pre-load and strain the membrane with a substantially marked strain. Such a strain, by itself, limits the remaining dynamic range that would be left for later movements of the membrane (as required for the regulating action and for its retreat if a clog is created).
It is obviously clear that if it is desired that the non-drain valve should close down and seal the flow passage through it at relatively high pressure values that prevail in the water supply conduit line, then it is required to strain the membrane with a larger “biased” (preset) stress. This pre-loading strain would eventually limit the dimensions of the water flow passage into the drip emitter on opening of the non-drain valve, and simultaneously constrain the dimensions of the water flow passage towards the water outlet from the drip emitter (a passage that is required, as said, to have an as large as practicable size in order to gain an effective self flushing action).
Thus, exploiting the same membrane to accomplish two goals—to perform the regulation operation and to serve as a seal of the non-drain valve, was found to be associated with considerable difficulties that might even harm the unmistakably clear advantages of the differential regulation principle and impart constraints on advanced design of the throttle means in drip emitters. As a consequence, the utilization of the same membrane for the two functions as suggested,—i.e. regulation and seal in the non-drain valve, does not provide an answer to the requirements of the agriculture community, that the non-drain valve would enable closing the drip emitter and prevent drainage through it, even at relatively high pressure values that prevail in the water supply conduit—three to seven (3-7) meter. According to the best available knowledge of the applicant, regulated drip emitters equipped with a non-drain valve, of the type that is installed within the water supply conduit and as an integral part thereof, enable nowadays closing of the non-drain valve solely for a relatively low pressure of about one to three (1-3) meter.
Eckstein's patent U.S. Pat. No. 5,615,838 described a regulated drip emitter of the type that is affixed to the inner wall of the water supply conduit (inserted during the manufacturing process of the conduit, for example—by extrusion,) and includes a non-drain valve. In the configuration illustrated in the patent (see there, FIG. 1 and FIG. 3), the regulating function is carried out by resorting to increasing or decreasing the affective length of the throttle means. The elastomer component in there serves for increasing or decreasing the effective length of the throttle means by using several valves that are located along the throttle means. A rise of the water pressure within the water supply conduit stresses the elastomer component to a gradual progressing closing of the valves array and as a consequence of this, to direct the water flow to pass through a longer throttle means.
Referring to FIG. 1b. This figure constitutes a general schematic view of a drip emitter 25 in accordance with the above cited prior art (and see FIG. 1 in above cited patent). Drip emitter 25 includes a water inlet 27 that is connectable to a water passage from the water supply conduit (that is not illustrated) into the drip emitter. Two water outlet openings 31 and 29 are connected between them, and couple to a flow passage from the drip emitter towards the surface area intended to be irrigated. An elastomer portion 33 is strained and biased against the water inlet opening 27 for creating non-drain valve 35. Throttle means 37 is provided in order to reduce the water pressure. The latter is formed as a plurality of throttle means sectors 37a to 37d that are inter connected one to the other in series. Upon opening non-drain valve 35, throttle means 37 is connected to a flow passage into it from water inlet 27 and to the water exit from it, after the water pressure is reduced, toward water outlets openings 29 and 31. Elastomer portions 39a to 39c constitute regulating membranes that upon opening of the non-drain valve 35, their one side is exposed to the water pressure prevailing in the water supply conduit and their other side is exposed to the various water pressure values that prevail at different points along throttle means 37, so that regulating membranes 39a to 39c have become moveable in order to increase or decrease the effective length of throttle means 37. In other words, the rise of the water pressure in the water supply conduit stresses elastomer portions 39a to 39c to affect a gradual progressive closing of the valves and as a consequence of this, to route the water flow so that the water passage through throttle means 37 is longer. A constructional characteristic of drip emitter 25 is the utilization of a single elastomer component—namely component 41, so that different portions of it are designated for serving as seal 33 of the non-drain valve and for the needs of the regulating membranes 39a to 39c. 
The ensuing drawback is that drip emitter as per this prior art is prone to malfunctions because a relatively narrow flow passage is formed in the non-drain valve. A narrow flow passage that may be suffices for passing the required throughput but might lead to the danger of accumulating contaminants already at the non-drain valve location. From the instant that non-drain valve 35 is opened, the water pressure that prevails on the two sides of elastomer portion 33 would be substantially similar and in this state, a relatively narrow water inlet passage would result, and as much as one desires to use the mechanism described there, at high opening-closing pressures, so would the passage become narrower and an unwanted phenomena of choking the elastomer portion at a high rate towards water inlet opening 27 will occur. In other words, in the configuration described in the cited Eckstein's patent, removing the seal from non-drain valve 35 and allowing flow passage through it at its open state, depends on the capability of the force that is exerted by the water pressure prevailing at the water supply conduit to overcome, first, the strain at which membrane 33 was biased towards water inlet 27, and then (later, in order to continue and leave the valve at the open state), also on the force that the water pressure exerts after the water passed the non-drain valve on the other (second) side of the same membrane 33 itself.
Moreover, a selection—if it would be made, by a professional in this field of the preferred embodiment described in the above cited patent (see there, FIG. 3), poses the professional vis a vis a dilemma (problem) similar to the one described above when referring to Mehoudar's patent U.S. Pat. No. 5,279,462, namely, whether to focus on optimal design of a given membrane as the regulating membrane, or may be to focus on its design to suit it properties as the seal of the non-drain valve. In the configuration described in Eckstein's patent with reference to FIG. 3 there, one of the portions of the elastomer component that serves also as one of the regulating membranes, doubles as being also the seal of the non-drain valve (see there, component marked 68). Any professional in this field would understand that any one of the regulating membranes of drip emitter as per Eckstein's patent might perform the gradual closing and opening of a flow passage. It is required to perform this operation at defined pressures and at a defined rate (relative to the increase of the water pressure prevailing in the water supply conduit or to its decrease). This requirement contradicts the requirement that when functioning as a non-drain valve seal, the same membrane should perform complete opening or closing operation, at a defined pressure that might be relatively high.
Regulated drip emitters that are also of the type that is affixed to the inner wall of the water supply conduit are described in Cohen's patent U.S. Pat. No. 6,302,338. In these drip emitters the functions of the regulation action and that of the non-drain property were separated. This is achieved by using two separate and dedicated elastomer components, one as the regulating membrane and the other as the non-drain seal. In the configuration described in the patent, the regulating function is taken care of by an approach of increasing or decreasing the dimensions of the flow passage that is formed along the throttle means.
Referring to FIG. 1c. This figure constitutes a general schematic view of a drip emitter 45 in accordance with Cohen's patent. Drip emitter 45 comprises a water inlet opening 47 connectable to a water flow passage to the drip emitter from the water supply conduit (that is not illustrated) and a water outlet 49 that is connectable to a water flow passage towards the surface area intended to be irrigated. Connected in series one to the other in drip emitter 45 are preceding throttle means 51 and a following throttle means 53 intended for lowering the prevailing water pressure. The throttle means are connected to a water flow passage into them from water inlet 47 and to water flowing out from them after the water pressure was reduced, to water outlet opening 49. Also there is a first elastomer component 55 that in order to form a non-drain valve 56 is pre-strained and biased towards water inlet opening 47 (or—in the alternative illustrated there in FIG. 5, to the water outlet opening), from the instant that the water pressure in the water supply conduit drops to below a pre set threshold value. A second elastomer component 57 serves as the regulating membrane—on its one side it is exposed to the water pressure prevailing in the water supply conduit (see arrow numbered 58) and on its second (other) side—to the water pressure that gradually decreases as it passes through throttle means 53, and is moveable in order to reduce or increase the dimensions of the flow passage that is formed in throttle means 53.
The ensuing drawback is that resorting to use two different elastomer components causes an increase of the manufacturing and assembling expenditures of the drip emitters (obviously—as an additional elastomer component is added). Moreover, similarly to what was explained above when referring to Eckstein's patent U.S. Pat. No. 5,615,838, in the present case too, a drip emitter in accordance with this prior art is prone to the formation of a relatively narrow flow passage in the non-drain valve. Such a narrow flow passage that may be suffices for passing the required water quantity throughput but might lead to the danger of accumulating contaminants already at the non-drain valve space. From the instant that non-drain valve 56 is opened, the water pressure that would prevail on the two sides of elastomer component 55 would be approximately similar one to the other and in this state of affairs, a relatively narrow water inlet passage would result, and as much as one desires to use the mechanism described there with high opening-closing pressures, so would the passage become narrower and an unwanted phenomena of the choking elastomer component at a high frequency, towards water inlet opening 47 would occur. In other words, in the configuration described in Cohen's patent, removing the seal from non-drain valve 56 and allowing flow passage through it at its open state, is depends on the capability of the force that is exerted by the water pressure prevailing at the water supply conduit to overcome, first, the strain at which membrane 55 is biased towards water outlet opening 47, and then (later, in order to continue and leave the valve at the open state), also overcome the force that exerted by the pressure of the water that passed through the non-drain valve on the other (second) side of the same membrane 55 itself.
Further more, a selection—if it would be made, by a professional in this field of the preferred embodiment described in Cohen's patent (see there, in FIG. 1b), would even worsen the prevailing condition. Cup 50 that is described in the cited patent as the non-drain valve's seal, due to the specific structure of its configuration (as a cup with a “skirt 52” around its edges—see there), hinders the opening of a large flow passage and increases the choking phenomena at high frequency towards the water inlet opening.